Periods of water surplus and deficit in Northern California follow a pronounced quasi-decadal cycle. This cycle is largely driven by the frequency of atmospheric rivers (ARs), affecting the region’s wet and dry periods. Our analyses demonstrate that the quasi-decadal cycle of AR frequency relies on moisture transport associated with the position and intensity of the Aleutian Low. In observations, the Aleutian Low is shown to covary with tropical Pacific sea surface temperature anomalies. A modeling experiment, which incorporates ocean observations from the equatorial Pacific into the fully coupled climate model, provides support that the quasi-decadal cycle of the Aleutian Low is forced by the tropical Pacific. Subsequently, the tropical Pacific modulates the wet season moisture transport toward California on decadal time scales, affecting AR frequency. These results provide metrics for improving interannual-to-decadal prediction of AR activity, which drives hydrological cycles in Northern California.
Jacbon Stuivenvolt-Allen: https://orcid.org/0000-0002-2611-284X
Shih-Yu Simon Wang: https://orcid.org/0000-0003-2009-2275
Zachary Johnson: https://orcid.org/0000-0003-0314-706X
Yoshimitsu Chikamoto: https://orcid.org/0000-0003-1001-5188
An edited version of this paper was published by AGU. Copyright (2021) American Geophysical Union.